Rotary drum type pelletizing apparatus



June 7, 1955 J. E. WIKLUND ROTARY DRUM TYPE PELLETIZING APPARATUS 5 Sheets-Sheet 1 Filed July 3, 1952 wa Q MV J. E. WIKLUND ROTARY DRUM TYPE PELLETIZING APPARATUS June 7, 1955 Filed July 5, 1952 3 Sheets-Sheet 2 June 7, 1955 J. E. WIKLUND ROTARY DRUM TYPE PELLETIZING APPARATUS 3 Sheets-Sheet 3 Filed July 5. 1952 ROTARY DRUM TYPE PELLETIZING APPARATUS Johan Eiof Wilrlund, Halsinghorg, Sweden, assignor to Reyniersholms Gamla lndustri Aktiebolag, Halsingborg, Sweden, :1 company of f'iweden Application July 3, 1952, Serial No. 297,119

Claims priority, application Sweden July 4, 1951 13 Claims. (Cl. 18-1) The present invention relates to the manufacture of pellets by rolling pulverulent material in rotary drum and is particularly concerned with the pelletizing of pulverulent or fine-grained ores. It is particularly suitable for pelletizing roasted pyrite and may with advantage be employed for lead ore concentrates, such as lead sulphide.

The primary object of the invention is to produce pellets without returning unpelletized material and undersized pellets as is necessary in all prior methods known to applicant. Another object is to obtain pellets of uniform size. A further object is to perform the pelletizing in two stages by first creating nuclei in a separate drum.

These objects and other advantages that will be easily understood by those familiar with the present art will be obtained according to the invention by using drums having the form of a frustum of a cone and arranging the central axis of the drum at an adequate inclination to the horizontal plane with the wide end of the drum at a higher level than the small end.

The invention will now be described with reference to the accompanying drawings illustrating the principle of the invention and some embodiments thereof, it be ing, however, understood that the invention is not limited to the embodiments illustrated.

In the drawings:

Fig. 1 illustrates the theory of the invention.

Fig. 2 is a vertical section, through the longitudinal axis, of apparatus constituting the preferred embodiment of the invention; Fig. 3 is a plan View of a modification of the embodiment shown in Fig. 2, whereas Fig. 4 is a frontal view thereof and Pig. 5 a vertical section along the line d-5 in Fi g. 2. Fig. 6 illustrates a screening device employed in the embodiment of Fig. 2.

Fig. 7 illust ates an embodiment in which two drums according to the invention are employed in series.

Referring first to Fig. l, the invention is based on the theory that, due to the conical shape of the drum and the inclination of the central axis M thereof relative to the horizontal plane H with the wide end of the drum at a higher level than the small end, the pulverulent material supplied to the drum and pellets formed therein can be suitably distributed in the length direction of the drum and the non-pelletized pulverulent material be moved within the drum in opposite direction to the pellets to be discharged. The apex angle of the drum cone is 2/3 and the central axis is supposed to form an angle a with the horizontal plane. The inclination 0 must be less than half of the apex angle, that is a f]. Supposing that a particle is situated at the point marked A, this particle upon rotation of the drum and due to the friction against the wall of the drum will follow the wall and move in a plane perpendicular to the central axis until it reaches point B from Where, due to gravity, it will fall down along the slope of the material the shortest way towards the bottom of the drum to point C in a vertical plane perpendicular to the horizontal plane.

2,709,833 Patented June 7, 1955 As will be evident from Fig. 1, this vertical plane forms the angle a with the plane along which the particle was lifted from point A to point B. When returned to the bottom at point C, the particle has moved a distance towards the apex of the cone, the magnitude of the distance being a function of the angle at but being independent of the apex angle 2/3. As the height to which the particle will be lifted, that is the position of point B, is dependent on the degree of filling of material in the drum, the position of point C will also be a function of said filling. In case the particle is a pellet or, generally speaking, is rounded off, it will also follow the way described from A to B and from B to C but when arrived at C it will have a tendency to roll on the bottom or" the drum in a direction from the apex of the cone because the bottom is sloping by an angle 'y being the difference between the angles 5 and u. The larger pellets, the greater is the tendency to move in said direction. Therefore, the larger pellets will collect at the wide end of the cone and smaller pellets remain in earlier sections of the cone until they have grown by picking up fine material to the size of the large pellets. The material wandering towards the apex of the cone will either form nuclei or meet nuclei formed near the apex. These nuclei grow successively by picking up line material and form ultimately a pellet which will have a tendency to wander towards the wide end of the cone as described.

The preferred embodiment of the pelletizing apparatus shown in Fig. 2 consists of a drum 1 in the form of a truncated cone of sheet metal. For some kinds of material, such as pulverized roasted pyrite, the drum for a capacity of about 3 tons an hour may have a length of about 3 meters, :1 diameter at the small end of 0.5 meter and a diameter at the wide end of 2 meters. The apex angle of the drum cone will then be about 28. The drum is provided with annular rings 4 and 5, by which the drum is supported on two pairs of flanged wheels 6 and 7, respectively. These wheels are journalled in bearings 3 secured to a frame structure 11 which is supported pivotally at the small end of the drum on a standard 12 about a shaft 13. At the wide end of the drum the frame 11 is supported by two screws 14 rotatable by hand-wheels 17 in axial bearings 15. The screws M are mounted in cars 16 having threaded bores matching the threads of the screws 14. By turning the wheel 1'7, the frame 31 can be raised or lowered until the drum axis will obtain the desired angle a relative to the horizontal plane.

At the one side of the drum the supporting wheels 6 and 7 are fixedly mounted on a common shaft 21 which is driven by a motor 22, mounted on the frame 11, over the belt 23 and the pulley 24. This belt and pulley transmission should preferably be of the type permitting variation of the gear so that the speed of rotation of the drum may be adjustable, such as between 3 and 10 revolutions per minute in a drum of the above dimensions.

At the wide end of the drum a discharge device in the form of a spiral grid 31 is provided which is best seen in Fig. 5. It is supposed that the drum rotates with the bottom portion in a direction from the spectator. As will be seen from Fig. 6, which illustrates the screen folded up, the screen consists of a plurality of supporting bars 32 secured to the end wall 3 of the drum. T 0 these bars a series of strings or threads 33 are secured as by welding. The threads may be 5 millimeters thick and should preferably be fitted at a distance of about 15 millimeters or, generally, at a distance equal to the minimum size wanted of the pellets. The width of the grid depends largely upon the capacity of the drum and it has been found that the width of 0.4 meter will be satisfactory at an output of up to at least 3 tons per hour, provided greases that the degree of selection of the drum is satisfactory. The grid has at the peripheral end a smaller shovel part 35, 36 which, in the embodiment shown, has a front part of impervious sheet material which is connected to the grid portion 36 of the shovel by a hinge 37 in a manner that the plate 35 can be rotated by the hand- Wheel 38 at the outside of the Wall 3 so as to be adjusted into a desired position relative to the peripheral wall of the drum in order that the degree of discharge can be regulated. The main portion of the grid is Wider than the shovel portion for the purpose of spreading out the pellets collected by the shovel so that the pellets can be effectively freed from adhering fine material and pellets which are too small may fall back into the drum when the grid upon rotation of the drum passes the pellets towards the center of the drum, where the pellets are discharged through opening 41 in end plate 3 and the short collar 42 to discharge board 43. For the purpose of keeping the pellets on the grid the latter is provided with a list 39. At its central end the width of the grid successively decreases in order to move the pellets care fully to the opening 41 so as to be discharged. Through the spiral form of the discharge grid the pellets are smoothly passed to the central discharge opening 41 and it is preferred to let the spiral pass through 360 so that the pellets will be discharged at about the same radius of the drum at which they were caught by the grid.

The drum now described is preferably put at an inclination of 5 to 7 at least when pelletizing roasted pyrite of relatively even grain size distribution and containing about 60% of a grain size less than 0.1 millimeter. In this connection, it should be noted that it is commonly considered necessary that roasted pyrite should contain more than 90% of grains less than 0.1 millimeter to be pelletizable.

The drum may be charged with pulverized material, such as roasted pyrite or iron ore, in any convenient manner through the small end 2 or through the dis charge opening 41 or through both, it being, however, advantageous to supply the charge near the discharge end of the drum. The distribution will then take place automatically as explained with reference to Fig. 1. Particularly in case the pellet nuclei shall be created in the drum itself, the finest material should preferably be supplied to the sections near the small end of the drum, which promotes the creation of nuclei, because in this section the charge is free from pellets which would crush the small nuclei.

, The charging of the drum will be best carried out h by the throwing apparatus illustrated in Figs. 2 and 3. This apparatus consists of a band 51 which is preferably only a few millimeters thick, such as 3 millimeters, and about 1 decimeter wide. This band is passed over a pulley 52, which is driven by a motor 53 over the belt 54 and pulley 55, and is further passed over the idlers 56 and 57, the latter of which being positioned at a level above pulley 52 and so far behind the latter as to permit a press roller 58 to be accommodated at about the same level as idler 57 between the latter and pulley 52 above the band 51 so as to press this band downwards to such an extent that the band will run on to pulley 52 in an approximately horizontal direction. The idler 57 and the press roller 58 are so closely positioned as to form a V-shaped space between the band 51 and roller 58. Roller 58 is provided with a groove 59 about 3040 millimeters wide and of about 10 millimeters depth. Pulley 52, idlers 56 and 57 and press roller 58 are rotatably mounted on shafts journalled in bearings 60 mounted in a stand wall 61. At the opposite side the pulley, idlers and roller are protected by a cover plate 62 which can be easily removed when, for instance, band 51 has to be exchanged.

Over the V-shaped space referred to above a hopper 65 is arranged for the material to be pelletized. The

hopper has lateral lips 66 forming side walls of the hopper in the V-shaped space.

When running at an appropriate speed, band 51 will throw the material fed into groove 59 with suflicient power into the drum so that the material Will be distributed and supplied to the sections best suited for the pelletizing operation. Due to the air resistance, a practical separation as to grain size will be obtained when the throwing apparatus is positioned at the small end of the drum. The coarser particles will reach the sections of the drum near the discharge end whereas part of the fine material will be upheld in the sections nearer to the small end 2.

The drum is preferably charged with so much material that in the sections near the discharge end of the drum the height of the charge reckoned along a radius will become about a quarter of the diameter of the drum,

the height decreasing successively towards the small.

end.

In some cases, it may be preferred to charge a minor portion, for instance, 2-l0% of the charge directly to the small end of the drum as over the feed board 71.

The pulverulent material is charged to the feeding apparatus through a hopper '72 over the turn-table 73 provided with a scraper 74 for feed board 71 and scraper 75 for feed hopper 65.

The creation of nuclei is promoted by increasing the speed of the turning-over of the bulk of the pulverulent material rolled in a drum. In the pelletizing of some materials or for speeding up the operation, it may, therefore, be advantageous to create nuclei in a separate drum especially adapted for the creation of nuclei. Such arrangement is illustrated in Fig. 7. The big drum 1 may be of the same size and structure as that described with reference to Figs. 26 and it may also be equipped with a throwing apparatus 50 of the same kind as that described above. The nucleus creating drum S1 is of a more compact shape than drum 1 and its drum cone has a greater apex angle than that of drum 1, for instance, being of the order of 60. The length of the drum may be about 1 meter and its inclination with regard to the horizontal plane may be about 10-15 As illustrated, the drum is rigidly secured at its small end 82 to a shaft 83 journalled in bearings 84 mounted on a frame 85. Shaft 83 is driven by motor 88 over belt 8? and pulley 90. The drum 81, once being positioned at an inclination suitable for the creation of the desired nuclei, usually need not be adjusted, and therefore, frame may be stationary. Nevertheless, the frame may be pivotable about shaft 91 secured to standard 92. At the opposite end a screw 14 may be arranged in the same manner as illustrated and described with reference to Fig. 2.

The drum 81 has a discharge grid 31 of the same type as described above and a discharge collar 42 for the nuclei to be discharged and fed to feed board 93 feeding the nuclei into the small end 2 of drum 1. Since the nuclei are very small as compared with the pellets formed in drum 1, the dimensions of grid 31, particularly the distance between the threads 33, have to be adapted to the minimum size Wanted of the nuclei.

The pulverulent material to be used for the creation of nuclei is fed through hopper 72 to turntable 73 and scraped olf by scraper 94 to be passed on to feed board 5 which is inserted into drum 81 through the discharge opening 41 thereof. The feed board 95 is pivoted to the frame 5 6 holding the turn-table 73 as by shaft 97.

The pivotal arrangement of board 95 makes it feasible to control to a certain extent the feed to the drum 81 so that the material can be supplied to an adequate section thereof. The turn-table 73 should be located so as also to supply the hopper of throwing apparatus 50.

What is claimed is:

l. Peiletizing apparatus comprising a drum having the form of a frustum of a cone and being positioned with its apex end downwards so that the central axis of such cone forms a positive acute angle of inclination with the horizontal smaller than half of the apex angle of such cone, support means for the drum, an end wall at least at the peripheral portions of the wide end of the drum, means adjacent an end of the drum for charging the latter with fine-grained material to be pelletized, means for discharging pellets from said peripheral portions of the wide end of the drum, and means for rotating the drum about its central axis.

2. Pelletizing apparatus as claimed in claim 1, in which the apex angle of said cone is greater than 6 and smaller than 70.

3. Pelletizing apparatus as claimed in claim 1, in which the apex angle of said cone is of the order 15 -to 40.

4. Pelletizing apparatus as claimed in claim 1 for preparing nuclei for pellets, in which the apex angle of said cone is of the order of 45 to 65.

5. Pelletizing apparatus as claimed in claim 1 further comprising a discharge grid projecting perpendicularly and inwardly from said end wall at the wide end of the drum, said grid extending spirally from a point near the periphery of the drum in the direction opposite to the direction of rotation of the drum to a point in the vicinity of the centre of the drum.

6. Pelletizing apparatus as claimed in claim 5, in which said end wall has a central discharge opening and the central end of said spiral discharge grid extends to said discharge opening.

7. Pelletizing apparatus as claimed in claim 5, in which said grid extends spirally through an angle of about 360.

8. Pelletizing apparatus as claimed in claim 5, in which the width of said grid is reduced at the peripheral end thereof.

9. Pelletizing apparatus as claimed in claim 5, in which the width of said grid successively tapers at the central end thereof.

10. Pelletizing apparatus as claimed in claim 5, in which said grid has a shovel at its peripheral end, said shovel being pivoted at the grid so as to make the distance of the edge of the shovel from the peripheral wall of the drum adjustable.

11. Pelletizing apparatus as claimed in claim 10, in which said shovel is secured to a shaft extending through said end wall, said shaft having means outside said end wall for its rotation for the purpose of adjusting the position of the shovel.

12. Pelletizing apparatus as claimed in claim 1, in which the charging means is a charging apparatus adjusted to supply the majority of the fine-grained material to sections of the drum at some distance from but near the wide end of the drum.

13. Pelletizing apparatus as claimed in claim 12, in which said charging apparatus is a throwing apparatus positioned at the small end of the drum.

Reterences Cited in the file or". this patent UNITED STATES PATENTS 773,356 Waggoner Oct. 25, 1904 987,554 Coggeshall Mar. 21, 1911 1,695,362 Bourges Dec. 18, 1928 1,921,114 Brackelsberg Aug. 8, 1933 1,931,499 Klugh Oct. 24, 1933 2,158,513 Lloyd May 16, 1939 2,268,816 Gabeler et a1 Jan. 6, 1942 2,436,771 Hood Feb. 24, 1948 

